The large majority of intraocular tumours can be diagnosed quite reliably by ophthalmoscopy and ultrasonography. Biopsy is useful for the rare instance when there is considerable doubt about the diagnosis despite full clinical examination.


Trans-vitreal biopsy

This is performed by passing either a fine 25-gauge needle or a 25-gauge vitreous cutter (like a vacuum cleaner) through the eye into the middle of the tumour and taking small samples for analysis. The vitreous cutter gives a better yield so that it is more reliable. One might imagine that passing a needle through the retina would inevitably cause a retinal detachment, but this complication is surprisingly rare. There is often a mild haemorrhage, which can cause blurred vision or floaters, but this usually resolves spontaneously in a short time.



The picture shows trans-retinal biopsy in progress.


Trans-scleral fine needle aspiration biopsy

A fine, sharp needle is passed through the wall over the eye directly into the tumour to obtain a tiny sample. This procedure is performed to grade the malignancy of an intraocular melanoma, if the tumour is located towards the front of the eye and if treatment consists of plaque radiotherapy.


Incisional biopsy

Incisional biopsy is performed by creating a small trapdoor directly over the tumour and removing a small sample with scissors. This is a more difficult procedure than trans-ocular biopsy and is usually performed under general anaesthesia, with moderate lowering of the blood pressure. There is a small risk of seeding tumour cells into the normal tissues around the eye and if the tumour is not treated quickly it may spread through the opening created by the surgery. For these reasons, a ruthenium plaque is usually placed over the area of the biopsy during the same procedure, selecting the time for which the plaque is left in place according to the diagnosis of the tumour.


Excisional biopsy

Excisional biopsy involves total removal of the tumour, thereby providing both a diagnosis and a cure. It is mostly performed if local resection would be the treatment of choice in any case. In exceptional situations, if the eye is blind and painful the most practical solution is to remove the eye and to establish the diagnosis by pathological examination.